1. Field of the Invention
The present invention relates to a code acquisition device and method using a two-step search process in a Direct Sequence-Code Division Multiple Access (DS-CDMA) Ultra Wide Band (UWB) modem, and more particularly, to a code acquisition device and method using a two-step search process in a DS-CDMA UWB modem in which when a beacon frame synchronization being a super-frame timing synchronization is performed, twenty-four noncoherent correlators are used in a first search process to search for an allocation code allocated to a piconet, and a spread code sequence searched in the first search process is used in a second search process to concurrently decide a super frame time (packet code) and a symbol boundary time (firstly received path).
2. Description of the Related Art
As well known, in a conventional DS-CDMA system, pilot signals all having patterns of “0” can be always radiated from a base station, and if code synchronization is acquired through the pilot signal, a reception packet time of a type allocated to a PN code chip clock is automatically acquired. Accordingly, in a conventional DS-CDMA system of Data Communication Network (DCN), Personal Communication Services (PCS), International Mobile Telecommunications-2000 (IMT-2000), if only the code synchronization is acquired, a relation of a period of a PN code sequence, a chip duration and the like can be used to acquire a packet synchronization.
However, unlike the conventional DS-CDMA system, in a DS-CDMA UWB modem of IEEE 802.15.3a, when a device belonging to a piconet is turned on, the device should primarily receive a beacon frame to communicate with a piconet coordinator. Before the reception, code synchronization is performed between a spread code sequence received from the piconet coordinator and a spread code sequence generated from a device receiver. Additionally, since a spread code of the piconet relating to the code synchronization, a packet synchronization (super frame time decision), and a symbol boundary time for allocating a code phase to a plurality of fingers should be searched within a determined preamble duration, a code synchronization acquisition process should be necessarily performed at a high speed.
However, a device and method for performing a code synchronization acquisition at the high speed in the DS-CDMA UWB modem of the IEEE 802.15.3a has not been developed. Just only analogous type of searcher is embodied by Motorola Corporation, but a digital type of searcher for a reception signal does not have ever been proposed before. Accordingly, there is a drawback in that it is difficult to perform a communication between the device belonging to the piconet and the piconet coordinator due to the absence of a kernel technology of the DS-CDMA UWB modem.